The Influence Of Warm Deformation On The Microstructure And Properties Of Multi-scale Lamellar Fe-C Alloys

The plain Fe-C alloy is widely used in constructional steel and mechanical components.For the purpose of economic efficiency and optimization of service performance,the C45 steel was selected to construct a heterogeneous structure,which reduces the addition of alloy elements and significantly improves the overall mechanical properties of the material.The microstructure characteristics of the experimental steels were characterized by SEM and EBSD techniques,and the microscopic deformation mechanism and macroscopic mechanical behavior of the experimental steels were analyzed qualitatively and quantitatively by combining KAM,GOS,and TF methods.A lamellar structure with different grain size distributions was obtained,the ferrite matrix of the experimental steel spans three grain levels.The sample with a temperature deformation of 84% had a tensile strength of 1173 MPa and a total elongation of 8.4%,after annealed,it reached a tensile strength of 778 MPa while maintaining 13.4% of the tensile strength.The steel with a warm deformation of 84% showed the best strong plastic matching after warm rolling and annealing.At the same time,in the Charpy impact test at different temperatures,the sample deformation to 84%showed good impact resistance.The idea of calculating grain boundary strengthening based on the grain level and using the mixing rule is proposed.When calculating the grain boundary strengthening increment of the annealed sample,a correction coefficient is set to obtain the effective grain size in the actual sense.It proves the existence of additional strengthening mechanism and interface effect.The warm-rolled and annealed samples with 84% deformation show the highest additional strengthening value,and the SHR curve of the warm-rolled sample shows secondary hardening.The study found that the increase of deformation reduce the volume fraction of cementite,and the phenomenon of resolution occurs,and then nano cementite is precipitated during the annealing process.The necessary condition for multi-scale lamellar Fe-C alloys to obtain high-strength plasticity is obtains about 50% of the MG volume fraction and the UFG volume fraction as high as possible in soft ferrite phase.Figure 51;Table 13;Reference 107...